When scrapped automobiles are shredded to recover ferrous and non-ferrous metals, large quantities of non-metallic solid waste are generated consisting mainly of rubber and plastic materials. The disposal of this material presently requires the use of valuable land-fill sites and constitutes the waste of potentially valuable resources. Pyrolysis, i.e., thermal decomposition in the absence of oxygen, of these mainly organic wastes into char and gaseous and liquid chemicals is one approach to an ecologically responsible as well as a profitable means of recycling both energy and chemical materials.
Pyrolyzed shredder waste has been shown to yield substantial amounts of highly aromatic pyrolysis oil from which chemical materials such as benzene, toluene and xylene can be produced. Often, however, processes developed for the pyrolysis of plastic and rubber wastes have as their objective the generation of oil products which can be used as fuel oils, i.e., for their energy content. The gaseous products produced by such processes are generally simply combusted prior to release into the atmosphere. Advantageously, these gases have been burnt to generate heat for the pyrolytic or other processes. Undesirable conversion products such as e.g., ammonia, sulfur or acidic materials which may be present in the oil or gas can be removed by adding reactive chemicals to the waste or by scrubbing the volatilized products.